Understanding Bell’s palsy.

Bell’s palsy is a form of temporary facial paralysis resulting from damage or trauma to the facial nerves. The facial nerve, also called the 7th cranial nerve, travels through a narrow, bony canal in the skull, beneath the ear, to the muscles on each side of the face.

When Bell’s palsy occurs, the function of the facial nerve is disrupted, causing an interruption in the messages the brain sends to the facial muscles. This interruption results in facial weakness or paralysis.

It is named for Sir Charles Bell, a 19th century Scottish surgeon who described the facial nerve and its connection to the condition. Generally it affects only one side of the face; in rare cases it can affect both.

Symptoms vary from person to person and range from mild weakness to total paralysis. They may include twitching, weakness or paralysis on one side of the face, drooping of the eyelid and corner of the mouth, drooling, dryness of the eye or mouth, impairment of taste, and excessive tearing in one eye. They usually begin suddenly and reach their peak within 48 hours.

Other symptoms may include pain or discomfort around the jaw and behind the ear, ringing in the ears, headache, hypersensitivity to sound on the affected side, impaired speech, dizziness, and difficulty eating or drinking.

The exact cause is not known. Viral and immune disorders are often implicated, and there may be an inherited tendency. Symptoms develop due to a deficiency of blood supply and pressure on the 7th cranial nerve as a result of nerve swelling.

Bell’s palsy affects approximately 40,000 Americans each year. It affects men and women equally and can occur at any age, but is less common before age 15 or after age 60. It disproportionately affects people who have diabetes or upper respiratory ailments such as the flu or a cold.

Diagnosis is made from the clinical presentation, including a distorted facial appearance and the inability to move muscles on the affected side, and by ruling out other possible causes of facial paralysis. There is no specific laboratory test to confirm it.

A clinician examines for upper and lower facial weakness. Electromyography (EMG) can confirm nerve damage and its extent. Blood tests can help find concurrent problems such as diabetes and certain infections, and MRI or CT scans can rule out other structural causes of pressure on the facial nerve.

Bell’s palsy affects each person differently. Some cases are mild and symptoms subside on their own within about two weeks. For others, treatment may include medications and other therapies. Steroids such as prednisone are used to reduce inflammation, and antivirals such as acyclovir may help shorten the course. Anyone taking prescription medicines should talk to their doctor before taking over-the-counter drugs.

Eye protection matters. Bell’s palsy can interrupt natural blinking, leaving the eye exposed to irritation and drying. Lubricating drops, ointments or gels and eye patches are effective, especially at night.

Physical therapy, facial massage or acupuncture may provide a small improvement in facial nerve function and pain. Decompression surgery is controversial and seldom recommended; on rare occasions reconstructive surgery may be needed.